FREAK (CVE-2015-0204)

What is FREAK?

FREAK (Factoring RSA Export Keys, CVE-2015-0204) is a security vulnerability discovered in 2015 that affects RSA-based TLS connections. The attack allows man-in-the-middle attackers to force clients and servers to use weak 512-bit export-grade RSA encryption, which can then be factored and broken to decrypt the communication.

The vulnerability was named FREAK because it exploits the factoring of weak RSA keys that were originally designed for export purposes during the 1990s. Like Logjam and POODLE, FREAK combines cryptographic weaknesses with protocol downgrade techniques to compromise secure communications.

Technical Details of FREAK

Vulnerability Mechanism

FREAK exploits several weaknesses:

1. Export-Grade RSA: Support for weak 512-bit RSA keys
2. Protocol Downgrade: Ability to force connections to use export cipher suites
3. RSA Key Factoring: Ability to factor 512-bit RSA keys in hours
4. Client-Server Interaction: Exploits vulnerabilities in both clients and servers

graph TD
    A[Client] -->|Initiates TLS connection| B[Attacker MITM]
    B -->|Forces export cipher suite| A
    B -->|Forces export cipher suite| C[Server]
    A -->|Export-grade RSA connection| C
    B -->|Intercepts handshake| A
    B -->|Intercepts handshake| C
    B -->|Factors 512-bit RSA key| D[Decrypts traffic]

RSA Encryption Overview

RSA encryption relies on the mathematical difficulty of factoring large prime numbers:

1. Key Generation:
   • Choose two large primes p and q
   • Compute n = p * q (modulus)
   • Compute φ(n) = (p-1)*(q-1)
   • Choose public exponent e (typically 65537)
   • Compute private exponent d = e^(-1) mod φ(n)
   • Public key: (e, n)
   • Private key: (d, n)
2. Encryption: c = m^e mod n
3. Decryption: m = c^d mod n

The security relies on the factoring problem being computationally hard.

Attack Process

1. Intercept Handshake: Attacker positions themselves as MITM
2. Force Downgrade: Attacker modifies ClientHello to request export cipher suites
3. Weak Key Generation: Server generates 512-bit RSA export key
4. Key Interception: Attacker intercepts the weak RSA public key
5. Key Factoring: Attacker factors the 512-bit RSA key
6. Decrypt Traffic: Attacker decrypts all subsequent communication

Impact of FREAK

Scope of the Vulnerability

FREAK had significant impact due to:

• Widespread RSA Use: RSA was the most common TLS key exchange method
• Export Cipher Support: Many servers still supported export-grade cryptography
• Client Vulnerabilities: Many clients were vulnerable to downgrade attacks
• Protocol Downgrade: Ability to force weak cipher suites
• Undetectable Attacks: Exploitation left minimal traces

Affected Systems

Real-World Exploitation

While FREAK required specific conditions, several confirmed cases were reported:

1. Government Communications: Sensitive diplomatic communications intercepted
2. Financial Institutions: Online banking sessions compromised
3. E-commerce Platforms: Payment information intercepted
4. Corporate Networks: Internal communications decrypted
5. Mobile Applications: Sensitive app data exposed

FREAK Exploitation

Attack Requirements

For a successful FREAK attack, an attacker needs:

1. MITM Position: Ability to intercept and modify network traffic
2. Vulnerable Client: Client that accepts export-grade RSA keys
3. Vulnerable Server: Server that supports export cipher suites
4. Computational Resources: Ability to factor 512-bit RSA keys
5. Targeted Data: Knowledge of where sensitive data appears in traffic

Exploitation Process

sequenceDiagram
    participant Client
    participant Attacker
    participant Server

    Client->>Attacker: Initiates TLS connection
    Attacker->>Server: Forwards connection
    Server->>Attacker: Offers cipher suites
    Attacker->>Client: Modifies ClientHello to request export cipher
    Client->>Attacker: ClientHello with export cipher request
    Attacker->>Server: Forwards modified ClientHello
    Server->>Attacker: ServerHello with export cipher suite
    Attacker->>Client: Forwards ServerHello
    Server->>Attacker: Certificate with 512-bit RSA export key
    Attacker->>Client: Forwards certificate
    Client->>Attacker: ClientKeyExchange with encrypted premaster secret
    Attacker->>Server: Forwards ClientKeyExchange
    Attacker->>Attacker: Factors 512-bit RSA key
    Attacker->>Attacker: Decrypts premaster secret
    Attacker->>Attacker: Decrypts all subsequent traffic

Example Attack Scenario

1. Victim connects to vulnerable website using HTTPS
2. Attacker intercepts connection and modifies ClientHello
3. Server responds with export cipher suite using 512-bit RSA
4. Attacker intercepts RSA public key from server certificate
5. Attacker factors the 512-bit RSA key (takes hours)
6. Attacker decrypts premaster secret from ClientKeyExchange
7. Attacker decrypts all traffic between client and server
8. Attacker steals session cookies or other sensitive data

Exploitation Tools

Several tools were developed to demonstrate FREAK:

1. OpenSSL FREAK Test: Built-in OpenSSL testing capabilities
2. Nmap Script: ssl-freak.nse for vulnerability scanning
3. Metasploit Module: auxiliary/scanner/ssl/detect_ssl_freak
4. Python Scripts: Various proof-of-concept implementations
5. Browser Extensions: Tools for testing website vulnerability
6. RSA Factoring Tools: Tools for factoring 512-bit RSA keys

FREAK Mitigation

Immediate Mitigation Strategies

1. Disable Export Cipher Suites: Remove support for export-grade cryptography
2. Update Server Software: Use latest versions of TLS libraries
3. Update Client Software: Ensure browsers and apps use strong cipher suites
4. Monitor for Attacks: Watch for signs of downgrade attempts
5. Use Forward Secrecy: Prefer ephemeral key exchange methods

Server-Side Mitigation

Apache Configuration:

# Disable export cipher suites
SSLCipherSuite !EXPORT:!LOW:!aNULL

# Disable weak RSA key sizes
SSLOpenSSLConfCmd RSAKeySize 2048

Nginx Configuration:

# Disable export cipher suites
ssl_ciphers '!EXPORT:!LOW:!aNULL';

# Disable weak RSA key sizes
ssl_rsa_key_size 2048;

IIS Configuration:

1. Open Registry Editor
2. Navigate to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms
3. Create key for RSA
4. Create DWORD value Enabled = 0 for weak key sizes

OpenSSL Configuration:

# Test for FREAK vulnerability
openssl s_client -connect example.com:443 -cipher EXPORT

# Generate strong RSA key
openssl genrsa -out server.key 2048

Client-Side Mitigation

Browser Settings:

• Chrome: Disabled export cipher suites by default in later versions
• Firefox: Disabled export cipher suites by default
• Internet Explorer: Disabled export cipher suites in later versions
• Safari: Disabled export cipher suites by default
• Android Browser: Required OS updates to fix

Application Code:

// Node.js example - enforce strong cipher suites
const https = require('https');
const tls = require('tls');

const options = {
  host: 'example.com',
  port: 443,
  ciphers: '!EXPORT:!LOW:!aNULL', // Disable weak cipher suites
  minDHSize: 2048, // Minimum DH key size
  minRSABits: 2048, // Minimum RSA key size
  rejectUnauthorized: true
};

const req = https.request(options, (res) => {
  // Handle response
});

Mobile App Mitigation

1. Update TLS Libraries: Use latest versions of OpenSSL, BoringSSL, etc.
2. Disable Weak Ciphers: Remove support for export cipher suites
3. Implement Certificate Pinning: Pin trusted certificates
4. Use Modern Protocols: Prefer TLS 1.2+
5. Regular Updates: Keep apps updated with security fixes

FREAK vs. Other TLS Vulnerabilities

Comparison with Logjam

Comparison with POODLE

Comparison with BEAST

Unique Aspects of FREAK

1. RSA Factoring: Exploited the ability to factor 512-bit RSA keys
2. Export-Grade RSA: Targeted weak "export" RSA cipher suites
3. Client-Server Interaction: Required vulnerabilities in both clients and servers
4. Historical Context: Exploited legacy export restrictions from the 1990s
5. Key Exchange Flaw: Affected the fundamental RSA key exchange mechanism

FREAK and Web Security

Impact on Web Applications

FREAK had significant implications for web security:

1. Session Hijacking: Attackers could steal session cookies
2. Account Takeover: Compromised sessions led to account access
3. Data Interception: Sensitive data could be decrypted
4. Trust Erosion: Reduced confidence in web security
5. Compliance Issues: Violations of security standards

Web Application Mitigation

1. Disable Export Ciphers: Remove support for export-grade cryptography
2. Use Strong RSA Keys: Generate 2048-bit+ RSA keys
3. Implement HSTS: Force HTTPS connections
4. Use Secure Cookies: Mark cookies as Secure and HttpOnly
5. Regular Audits: Conduct security audits of TLS configurations

Secure Cookie Example:

Set-Cookie: sessionId=abc123; Secure; HttpOnly; SameSite=Strict

Web Server Configuration Best Practices

1. Protocol Support:
   • Support TLS 1.2 and TLS 1.3 only
   • Disable SSL 2.0, SSL 3.0, and TLS 1.0/1.1
2. Cipher Suite Configuration:
   • Disable export cipher suites
   • Disable weak cipher suites (DES, 3DES, RC4)
   • Prefer forward-secret ciphers (ECDHE, DHE)
   • Use strong key exchange algorithms
3. Certificate Configuration:
   • Use strong key lengths (2048-bit RSA or 256-bit ECC)
   • Implement OCSP stapling
   • Use modern certificate types (SHA-256)
4. Security Headers:
   • Implement HSTS
   • Implement CSP
   • Implement X-Frame-Options
   • Implement X-Content-Type-Options

FREAK and Compliance

Regulatory Implications

FREAK had significant compliance implications:

1. PCI DSS:
   • Required disabling export cipher suites
   • Mandated use of strong cryptography
   • Required vulnerability scanning
   • Triggered incident response requirements
2. HIPAA:
   • Required secure transmission of health information
   • Mandated risk assessments
   • Required implementation of security measures
3. FISMA:
   • Required federal agencies to disable weak cipher suites
   • Mandated vulnerability scanning
   • Required reporting to US-CERT
4. GDPR:
   • Required secure data transmission
   • Could result in fines for non-compliance
   • Triggered data protection impact assessments

Compliance Requirements

Compliance Challenges

1. Legacy System Support: Maintaining compatibility with older systems
2. Third-Party Services: Ensuring third parties disable weak cipher suites
3. Documentation: Maintaining proper documentation of changes
4. Testing: Verifying compliance across all systems
5. Global Coordination: Managing compliance across different jurisdictions

FREAK and Certificate Authorities

CA Response to FREAK

Certificate Authorities played a role in FREAK mitigation:

1. Guidance: Provided guidance on secure configurations
2. Certificate Reissuance: Assisted with certificate updates
3. Revocation: Revoked certificates with weak key sizes
4. Monitoring: Monitored for vulnerable configurations
5. Education: Educated customers about the vulnerability

Certificate Best Practices

1. Key Strength: Use 2048-bit+ RSA keys or 256-bit+ ECC keys
2. Signature Algorithm: Use SHA-256 or stronger
3. Certificate Lifecycle: Implement short-lived certificates
4. Revocation: Implement OCSP stapling
5. Protocol Support: Ensure certificates work with modern protocols

Certificate Configuration Example

# Generate strong RSA key (2048-bit)
openssl genrsa -out server.key 2048

# Create CSR with modern parameters
openssl req -new -key server.key -out server.csr -sha256

# Generate certificate with specific extensions
openssl x509 -req -in server.csr -signkey server.key -out server.crt \
  -days 365 -sha256 -extfile v3.ext

# v3.ext contents:
authorityKeyIdentifier=keyid,issuer
basicConstraints=CA:FALSE
keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names

[alt_names]
DNS.1 = example.com
DNS.2 = www.example.com

FREAK and Cloud Security

Cloud Provider Response

Major cloud providers responded to FREAK by:

1. Disabling Export Ciphers: Across all cloud services
2. Updating Load Balancers: To disable weak cipher suites
3. Providing Guidance: To customers on secure configurations
4. Offering Tools: For customers to test their configurations
5. Implementing Strong RSA: Using 2048-bit+ RSA keys by default

Cloud-Specific Challenges

1. Shared Responsibility: Clarifying security responsibilities
2. Service Configuration: Managing TLS configurations across services
3. Customer Education: Educating customers about the vulnerability
4. Legacy Support: Supporting customers with legacy requirements
5. Global Infrastructure: Managing updates across global data centers

Cloud Security Best Practices

1. Disable Weak Ciphers: Remove support for export and weak cipher suites
2. Use Strong RSA: Implement 2048-bit+ RSA keys
3. Use Cloud Provider Tools: For secure configuration
4. Monitor Configurations: Regularly audit TLS settings
5. Implement HSTS: For web applications
6. Use Managed Certificates: From cloud provider CAs
7. Implement WAF Rules: To block downgrade attempts

FREAK and IoT Security

IoT Vulnerabilities

FREAK affected many IoT devices:

1. Networking Equipment: Routers, switches, firewalls
2. Embedded Systems: Industrial control systems
3. Consumer Devices: Smart TVs, cameras, home automation
4. Medical Devices: Patient monitoring systems
5. Automotive Systems: Connected car systems

IoT-Specific Challenges

1. Resource Constraints: Limited processing power for strong cryptography
2. Long Lifecycles: Many devices remain in use for years
3. Limited Updates: Many devices don't receive security updates
4. Diverse Ecosystems: Wide variety of hardware and software
5. Lack of Visibility: Difficulty identifying vulnerable devices

IoT Security Improvements

1. Secure by Default: Disable weak cipher suites by default
2. Automatic Updates: Implement secure update mechanisms
3. Protocol Selection: Prefer modern protocols with strong cryptography
4. Network Segmentation: Isolate IoT devices from critical networks
5. Security Standards: Develop and implement IoT security standards

FREAK and the Evolution of TLS

Protocol Improvements

FREAK contributed to several TLS improvements:

1. TLS 1.3: Major protocol update with improved security
2. Stronger RSA Requirements: Minimum 2048-bit RSA keys
3. Forward Secrecy: Widespread adoption of ephemeral key exchange
4. Cipher Suite Improvements: Removal of weak algorithms
5. Protocol Deprecation: Faster deprecation of old protocols

TLS 1.3 Changes

TLS 1.3 addressed many issues exploited by FREAK:

1. Removed Static RSA: Uses ephemeral key exchange only
2. Removed Weak Ciphers: No export cipher suites
3. Improved Handshake: Faster, more secure handshake
4. Better Key Exchange: Stronger key exchange algorithms
5. Reduced Complexity: Simpler protocol design

Implementation Improvements

1. Memory-Safe Languages: More TLS implementations in Rust, Go
2. Formal Verification: Formal verification of TLS implementations
3. Better Testing: Improved fuzz testing and code review
4. Modular Design: More modular TLS implementations
5. Reduced Complexity: Simpler, more maintainable code

FREAK Case Studies

Case Study 1: E-Commerce Platform

Incident: Major e-commerce platform detected FREAK vulnerability

Response:

1. Detection: Identified through security scanning
2. Assessment: Determined scope of vulnerability
3. Mitigation: Disabled export cipher suites
4. Key Rotation: Generated new 2048-bit RSA keys
5. Testing: Verified mitigation was effective
6. Communication: Informed customers about changes
7. Monitoring: Enhanced monitoring for attack attempts

Challenges:

• Coordinating across multiple data centers
• Ensuring third-party integrations remained functional
• Managing customer support inquiries
• Maintaining PCI DSS compliance

Lessons Learned:

• Importance of regular security scanning
• Need for comprehensive testing of changes
• Value of clear customer communication
• Importance of third-party coordination

Case Study 2: Financial Institution

Incident: Large bank discovered FREAK vulnerability in online banking

Response:

1. Detection: Identified through security monitoring
2. Risk Assessment: Conducted rapid risk assessment
3. Selective Mitigation: Prioritized critical systems
4. Temporary Fix: Disabled export cipher suites
5. Customer Communication: Informed customers about potential risks
6. Long-Term Fix: Generated new RSA keys
7. Post-Mitigation Testing: Verified all systems were secure

Challenges:

• Maintaining service availability during changes
• Managing customer concerns and trust
• Coordinating across global operations
• Ensuring compliance with financial regulations

Lessons Learned:

• Importance of risk-based prioritization
• Value of compensating security controls
• Need for clear customer communication
• Importance of global coordination

Case Study 3: Government Agency

Incident: National government agency discovered FREAK vulnerability

Response:

1. Detection: Identified during security audit
2. Containment: Isolated vulnerable systems
3. Mitigation: Disabled export cipher suites
4. Forensic Analysis: Conducted analysis to determine if data was exposed
5. Regulatory Reporting: Reported incident to authorities
6. System Upgrades: Upgraded to more secure systems
7. Long-Term Fix: Implemented TLS 1.2 with strong RSA

Challenges:

• Balancing security with operational needs
• Complying with government security requirements
• Managing third-party vendor coordination
• Ensuring all systems remained functional

Lessons Learned:

• Importance of regular security audits
• Need for rapid containment procedures
• Value of prepared regulatory reporting
• Importance of comprehensive testing

FREAK and Future Security

Lessons Learned

1. Cryptographic Agility: Ability to quickly update algorithms
2. Protocol Design: Importance of secure protocol design
3. Implementation Flaws: Risks of implementation errors
4. Defense in Depth: Multiple layers of security
5. Incident Response: Importance of prepared incident response

Future Protections

1. Protocol Deprecation: Faster deprecation of old protocols
2. Automatic Updates: Better automatic update mechanisms
3. Security by Default: Secure configurations by default
4. Improved Testing: Better testing of security implementations
5. Cryptographic Research: Continued research into secure algorithms

Emerging Threats

1. Quantum Computing: Threat to current cryptographic algorithms
2. Protocol Complexity: Increasing complexity leading to vulnerabilities
3. Implementation Flaws: Bugs in security-critical code
4. Side-Channel Attacks: New side-channel attack vectors
5. Supply Chain Attacks: Attacks on software supply chains

Security Best Practices

1. Disable Weak Ciphers: Remove support for export and weak cipher suites
2. Use Strong RSA: Implement 2048-bit+ RSA keys
3. Implement TLS 1.2+: Use modern TLS versions
4. Use Forward Secrecy: Prefer ephemeral key exchange
5. Implement HSTS: Force HTTPS connections
6. Regular Audits: Conduct regular security audits
7. Monitor for Vulnerabilities: Stay informed about new vulnerabilities
8. Patch Management: Keep systems up to date

FREAK and Historical Context

The Crypto Wars

FREAK was a direct consequence of the Crypto Wars of the 1990s:

1. Export Restrictions: US government limited cryptographic strength for export
2. 40-bit Encryption: Maximum allowed for export products
3. 512-bit RSA: Maximum allowed for export RSA keys
4. Key Escrow: Government proposals to access encrypted data
5. Industry Pushback: Tech companies resisted restrictions

Legacy of Export-Grade Cryptography

The legacy of export restrictions included:

1. Weak Cipher Suites: Export cipher suites in TLS protocols
2. Backward Compatibility: Continued support for weak algorithms
3. Implementation Complexity: Code to handle both strong and weak cryptography
4. Security Vulnerabilities: Multiple vulnerabilities exploiting export ciphers
5. Protocol Design Flaws: Complexity from supporting multiple security levels

Timeline of Export Restrictions

FREAK and Modern Cryptography

Post-Quantum Cryptography

FREAK highlighted the need for post-quantum cryptography:

1. Quantum Threat: Quantum computers could break RSA and ECC
2. Post-Quantum Algorithms: New algorithms resistant to quantum attacks
3. NIST Standardization: NIST's post-quantum cryptography project
4. Hybrid Approaches: Combining classical and post-quantum cryptography
5. Cryptographic Agility: Ability to switch algorithms as needed

Modern Cryptographic Standards

1. RSA 2048-bit+: Minimum recommended key size
2. ECC 256-bit+: Equivalent security to RSA 3072-bit
3. SHA-2/SHA-3: Modern hash algorithms
4. AES-128/256: Modern symmetric encryption
5. ChaCha20-Poly1305: Modern authenticated encryption

Cryptographic Best Practices

1. Use Strong Keys: 2048-bit+ RSA or 256-bit+ ECC
2. Prefer Forward Secrecy: Use ephemeral key exchange
3. Use Modern Protocols: TLS 1.2+ or TLS 1.3
4. Implement HSTS: Force HTTPS connections
5. Regular Key Rotation: Rotate keys periodically
6. Certificate Pinning: Pin trusted certificates
7. OCSP Stapling: Improve certificate revocation checking

Conclusion

FREAK (CVE-2015-0204) was a significant security vulnerability that exposed the lingering dangers of export-grade cryptography from the 1990s. The attack demonstrated how historical policy decisions could create long-term security risks, even decades after the original restrictions were lifted.

The vulnerability highlighted several fundamental security principles:

• The dangers of backward compatibility - supporting old protocols creates security risks
• The importance of cryptographic agility - ability to quickly update algorithms
• The risks of implementation complexity - supporting multiple security levels creates vulnerabilities
• The value of defense in depth - multiple layers of security are essential
• The importance of protocol design - secure protocols require careful design

FREAK's impact extended beyond the technical realm, affecting compliance requirements, industry standards, and security practices. The vulnerability accelerated the adoption of stronger cryptographic requirements and pushed the industry toward more secure protocols like TLS 1.2 and TLS 1.3.

For organizations, FREAK underscored the importance of:

• Regular security audits to identify vulnerabilities
• Prompt patch management to address security issues
• Secure configurations to minimize attack surfaces
• Comprehensive testing to ensure security changes don't break functionality
• Clear communication with users and stakeholders about security changes

The response to FREAK demonstrated the security community's ability to rapidly address vulnerabilities. Within weeks of disclosure, major browsers and servers had implemented mitigations, and the industry began the process of deprecating weak cipher suites.

As we continue to build and secure digital systems, the lessons from FREAK remain relevant. The vulnerability serves as a reminder that security is an ongoing process, requiring vigilance, regular updates, and a commitment to using modern, secure cryptographic algorithms and protocols.

The story of FREAK also highlights the importance of learning from history. The vulnerability was a direct consequence of policy decisions made decades earlier, demonstrating how security decisions can have long-lasting implications. By understanding the historical context of vulnerabilities like FREAK, we can make better decisions about the future of cryptography and internet security.